1. Field of the Invention
This invention relates to flame-retardant polymer compositions and to novel polymeric flame-retardant polymer additives and coatings for polymers in such forms as films and fibers and to processes for the preparation of said flame-retardant additives and coatings and non-burning fibers and films containing said flame-retardant additives and coatings.
More particularly, this invention relates to self-extinguishing and non-burning compositions comprising a normally flammable, linear high molecular weight polyester and a phosphorus- and halogen-containing flame-retardant polymer additive or coating.
2. Description of the Prior Art
It has long been considered desirable to impart flame-retardant qualities to polyester fibers and fabrics particularly those containing blends of polyester and natural fibers such as cotton and rayon so that they might be rendered non-burnable. Commercially, fiber forming polymers are prepared, for example, by the condensation of terephthalic acid or dimethyl terephthalate and a polymethylene glycol containing from about 2 to about 10 carbon atoms, particularly ethylene glycol, in accordance with U.S. Pat. No. 2,465,319. Fibers prepared therefrom are known to be rendered flame-retardant by incorporating therein polymeric or non-polymeric flame-retardant additive compounds by melt blending said additives with said polyester prior to formation of fibers and films by extrusion. A compound which has been suggested for the production of copolyester fibers and films having improved flame-retardance is 2,2-bis-[4,(2-hydroxyethoxy)-3,5-dibromophenyl]propane. Generally, 1 to 2 percent by weight of antimony oxide can be added to the flame-retardant films and fibers to further increase the flame-retardancy.
Alternatively, flame-retardant compounds such as tris(2,3-dibromopropyl)-phosphate have been extensively used either alone or in combination with other flame-retardant additives as flame-retardant coatings on fibers and films. The use of such non-polymeric flame-retardant additives is disadvantageous. The molecular entanglement that takes place with polymeric flame-retardant compounds does not take place with non-polymeric additives because of the relatively small size of these molecules. Relatively easy removal of these additives during use or upon washing in aqueous media thus results.
It is known to prepare flame-retardant unsaturated polyesters having phosphorus incorporated into the polyester chain and containing halogen derived from a halogenated dicarboxylic acid or halogen-substituted polyol as disclosed in U.S. Pat. Nos. 3,433,854 and 3,365,424. In addition to the use of flame-retardant additives and coatings to render polyesters flame-retardant, it is known to render cellulose acetate and cellulose triacetate flame-retardant for use in children's clothing and sleepwear, carpets and draperies, etc.
Because the extensively used tris(2,3-dibromopropyl)phosphate is considered to be carcinogenic, search continues to find improved additives capable of imparting flame-retardant properties to films and fibers of polyester and cellulose esters. Phosphorus- and halogen-containing polymers suitable for use as flame-retardant additives for normally flammable polymers are known from U.S. Pat. Nos. 4,030,933; 4,029,721; and German Offen. No. 2,608,785. However, there is no disclosure in the prior art of water-dispersible or water-soluble phosphorus- and halogen-containing polyesters capable of imparting flame-retardancy to normally flammable polymers.